1) Field of the Invention
The invention relates to an apparatus device for loosening scale in a borehole installation, more particularly an actuator provided with one or more cams arranged, by axial movement in the longitudinal direction of the apparatus, to move one or more cutting elements from a retracted passive state into a working position, the cutting element(s) projecting from an apparatus housing as the cutting element(s) is/are pressed against a surrounding tubular body from which scale is to be removed. The actuator is actuated mechanically by the tensioning of a line on which the apparatus is hanging or hydrostatically, for example, through coiled tubing to which the apparatus is connected.
In the recovery of hydrocarbon fluids from the underground, it is a known problem that substances carried in the fluid flow from the hydrocarbon-containing underground structure are deposited in the tubing by precipitation and deposition. The source of this problem may be substances existing in the structure, for example, substances dissolved in water accompanying the hydrocarbons, or it is substances which have been carried into the structure during production, for example salts in injection water pumped into the structure to increase the reservoir pressure. Common to the substances, which are the source of scale in the tubing, is usually that they are precipitated and deposited because of altered physical or chemical conditions as the fluid enters the tubing. Such a deposit may have ceramic properties, that is to say, it is hard and brittle—in the field also called “scale”—often in the form of calcium carbonate or calcium sulphate, or it may be in the form of paraffin wax which has a softer and tougher consistency. Common to such deposited products is that, over time, they reduce the flow from the hydrocarbon reservoir through the tubing to the surface.
2) Description of Related Art
Attempts have been made to solve the problem in different ways. One method includes the use of chemicals which are pumped down into the well to dissolve the scale so that it can be carried in the fluid flow out of the well.
Another method is mechanical cutting of the scale by means of a cutting tool which is passed through the tubing down to the production zone in question, where it is activated to work the scale inside the tubing. The pieces of scale material detached are carried in the fluid flow out of the well.
From U.S. Pat. No. 4,452,307 is known a reamer for removing paraffin, mineral scale, ice and other deposits from the inside of tubing or similar. A tapered housing provided with external cutting blades is set into limited rotation by gliding movement of the housing along a steep threaded connection between a central shaft and the housing. The rotational movement is achieved by repeated blows against the projecting end of the central shaft. The cutting blades thereby cut the deposits loose.
From U.S. Pat. No. 3,176,772 is known an arrangement of steel brushes which work a surrounding surface. U.S. Pat. Nos. 2,667,930 and 2,836,251 disclose spring-loaded scraping elements which work a surrounding surface by the rotating movement of an apparatus.
EP 516989 B1 discloses a pipe-cleaning device in which a cylindrical housing is provided with rotatable cutting elements disposed in recesses in the housing, the device being activated by a fluid flow through the pipe which is to be cleaned.
Further examples of the prior art in the field are FR 2543855 A1 and also U.S. Pat. Nos. 2,641,010, 4,920,600, 2,664,930 and 5,474,097.